Sanaa, Yemen (CNN) -- A mass of protesters took to the streets of Sanaa on Sunday to protest against a deal brokered by Persian Gulf nations that grants Yemen's president immunity from prosecution, witnesses said.

The protests spread across 14 provinces Sunday, according to witnesses and journalists on the ground. Witnesses reported hundreds of thousands of protesters in Sanaa alone.

On Saturday, Yemeni officials said the country's president, Ali Abdullah Saleh, had accepted a deal brokered by the Gulf Cooperation Council under which he would step down.

Both Saleh and the Yemeni opposition have agreed to the deal in principle. But Saleh has yet to sign the agreement, which stipulates he leave office within 30 days and provides complete immunity for him and those who served in his regime, said a senior foreign ministry official, who requested anonymity because he is not authorized to speak to the media.

The agreement also calls for a unity government to be formed within seven days.

Yaseen Noman, president of Yemen's largest opposition group, the Joint Meeting Parties (JMP) bloc, told journalists Saturday that members accepted the GCC proposal but had two comments -- they did not want to participate in a unified government, and they cannot force protesters to go home.

The Organizing Committee of the Youth Revolution denounced the proposal in a written statement Sunday.

"We the youth of revolution reject any proposal that does not hold Saleh accountable for the killing over 140 revolution protesters," the committee said.

The group also said it rejected the GCC proposal because it did not call for an immediate ouster of Saleh. The committee also said the GCC effort came to save the regime -- not to help the people.

Mohammed Albasha, spokesman for the Yemeni Embassy in Washington, said the opposition has to accept the final deal before Saleh will sign.

According to Yemeni government spokesman Abdu Ganadi, the ruling party said the opposition must accept the proposal completely or reject it -- partial agreements will not be accepted.

The GCC -- a bloc of six oil-producing Gulf nations -- has been working to ease tensions between Saleh and an increasingly restive opposition.

Previously, the opposition JMP bloc had objected to the Gulf initiative for failing to state clearly that Saleh must step down.

Even after agreeing to the deal, Saleh lashed out at the opposition, accusing them of "receiving dirty money to topple the government."

"We are very interested in preventing bloodshed because the Yemeni blood is very precious and the opposition can't drag us to killing each other," Saleh said. "Civil war will not only affect Yemen, but also the whole region and the international security.

He said the JMP was trying to grab power outside the framework of democracy.

"I am ready to quit, but according to the constitution, which stipulated change through the ballot boxes and free elections," he said.

Violent anti-government demonstrations have erupted for many weeks across Yemen and the chorus calling for Saleh's ouster has grown louder.

Saleh has been in power since 1978 and served as a staunch U.S. ally in the fight against al Qaeda in the Arabian Peninsula. He has argued he should stay in power because he is best equipped to fight Islamic militants.

He has also said he accepts opposition demands for constitutional reforms and holding parliamentary elections by the end of the year. He promised not to run for president in the next round of elections.

But earlier this month, Saleh said he would not offer any more concessions to those demanding reforms.